Power module operable in a hazardous environment

ABSTRACT

A power module and method of forming the same. The power module includes an extruded tube with internal and external fins, first and second opposing surfaces defining ends thereof, and an internal slot for housing a power converter. The power module includes a bottom plate having a first depression to receive a first O-ring to provide a first liquid-tight fluid seal at the first opposing surface for an electrically insulting oil encapsulating the power converter. The power module includes a cable interface plate having a second depression to receive a second O-ring to provide a second liquid-type fluid seal at the second opposing surface for the electrically insulting oil encapsulating the power converter. The power module includes an end cap to mate with the cable interface plate and accept a conduit fitting to enable an electrical cable to be routed from within the end cap to an external connection point.

The present application is a continuation of U.S. patent applicationSer. No. 16/949,625, entitled “Power Module Operable in a HazardousEnvironment,” filed Nov. 6, 2020, now U.S. Pat. No. 11,202,395, which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention is directed in general to power electronics and,more particularly, to a power module operable in a hazardousenvironment.

BACKGROUND

Power systems and modules are sometimes required to operate in physicallocations where flammable, explosive, or corrosive liquids and/orvapors, or flammable floating fibers are present, such as those definedin the National Electrical Code® ANSI/NFPA 70 as Class I, Division 2. Inthese conditions it is important that the power system does not presentan operating mode (normal or failure) that might ignite flammablematerials local to the power system. Likewise, the presence of theenvironmental conditions should not degrade the power system safetyprovisions such as insulation elements or safety management protectioncircuits.

A typical method for managing ac-dc power conversion applications foundin the industry today utilizes a non-regulated transformer-rectifiercircuit. Electrical components are submersed in a non-electricallyconductive oil bath in order to suppress any potential sparks orignition events that might occur during failure modes. Likewise, an oilbath also protects the electrical components from the localenvironmental conditions. Therefore, it is desirable to define anapproach that avoids limitations as listed hereinabove, and otherproblems that will be apparent to those skilled in the art. The listabove is not an exhaustive compilation of challenges for constructing apower system.

A power system and module is introduced that adapts high-frequency,switch-mode (“HFSM”) technology to environmentally challengingapplications, especially those where compliance with safety agencyhazardous location specifications, such as ISA-12.12.01 or UL 121201.Nonincendive electrical equipment for use in Class I and II, Division 2and Class III, Divisions 1 and 2 hazardous (classified) locations isdescribed by these specifications. These specifications cover units inlocations made hazardous by the presence of flammable gases, liquids,vapors, or fibers and where ignitable concentrations are not likely toexist under normal operating conditions, but can exist under certainconditions.

SUMMARY

These and other problems are generally solved or circumvented, andtechnical advantages are generally achieved, by advantageous embodimentsof the present invention for a power module and method of forming thesame operable in a hazardous environment. In one embodiment, the powermodule includes an extruded tube formed with an internal fin and anexternal fin and a first opposing surface and a second opposing surfacedefining ends of the extruded tube. The extruded tube also includes aninternal slot for housing a power converter. The power module includes abottom plate formed with a first depression configured to receive afirst O-ring disposed between the first opposing surface and the firstdepression to provide a first liquid-tight fluid seal at the firstopposing surface for an electrically insulting oil encapsulating thepower converter within the internal slot. The power module includes acable interface plate formed with a second depression configured toreceive a second O-ring disposed between the second opposing surface andthe second depression to provide a second liquid-type fluid seal at thesecond opposing surface for the electrically insulting oil encapsulatingthe power converter within the internal slot. The power module includesan end cap configured to mate with the cable interface plate and accepta conduit fitting to enable an electrical cable to be routed from withinthe end cap to an external connection point.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows can be better understood.Additional features and advantages of the invention will be describedhereinafter, which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed can be readily utilized as a basis formodifying or designing other structures or processes for carrying outthe same purposes of the present invention. It should also be realizedby those skilled in the art that such equivalent constructions do notdepart from the spirit and scope of the invention as set forth in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptionstaken in connection with the accompanying drawings, and which:

FIGS. 1 and 2 illustrate block diagrams of embodiments of power systemsin certified, explosion-proof housings;

FIGS. 3 and 4 illustrate block diagrams of embodiments of power systemsin a wall-mount cabinet fitted with cover;

FIG. 5 illustrates a schematic diagram of an embodiment of a powerconverter employable with a hazardous location environmentally sealedpower module;

FIG. 6 illustrates an isometric diagram of an embodiment of a hazardouslocation environmentally sealed power module;

FIG. 7 illustrates a partially exploded isometric diagram of anembodiment of a hazardous location environmentally sealed power module;

FIG. 8 illustrates an exploded isometric diagram of an embodiment of ahazardous location environmentally sealed power module;

FIG. 9 illustrates a plan view of an embodiment of an end cap; and

FIG. 10 illustrates a flow diagram of an embodiment of a method offorming a hazardous location environmentally sealed power module.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated, and cannot beredescribed in the interest of brevity after the first instance. TheFIGUREs are drawn to illustrate the relevant aspects of exemplaryembodiments.

DETAILED DESCRIPTION

The making and using of the present exemplary embodiments are discussedin detail below. It should be appreciated, however, that the embodimentsprovide many applicable inventive concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare merely illustrative of specific ways to make and use the systems,subsystems, and modules associated with a system and method for designof a power system and module operable in a hazardous environment.

A system will be described herein with respect to exemplary embodimentsin a specific context, namely, a broad class of power systems. Thespecific embodiments include, but are not limited to power systems andmodules coupled to an ac input voltage source and provide a dc outputvoltage. The principles of the present invention are applicable to otherpower system designs operable from a dc input voltage that may providean ac or a dc output voltage. A related power system is introduced inU.S. Pat. No. 9,353,446 entitled “Systems and Methods for ImpressedCurrent Cathodic Protection,” by Mulcahy, et al., issued May 31, 2016,which is incorporated herein by reference.

An objective of the disclosure is to provide a power system and modulethat converts locally available input power (which is typically acutility power) into a power type and magnitude more suitable to the endapplication, typically isolated, low voltage dc, in a manner that meetsthe requirements of typical hazardous environment safety standards fornonincendive equipment. Nonincendive equipment includes equipment whereany arc or thermal effect produced under normal operating conditions orotherwise, is not capable of igniting a flammable gas, vapor, dust-airmixture, fibers or flying particles surrounding the equipment.

The power system and module introduced herein address nonincendiverequirements through several design approaches. The internal circuitsemploy solid-state electronic switches that avoid sparking metalliccontacts involved in their operation. Field wiring is designed to beaccomplished external to the power system and module in a junction boxsuitable for the targeted installation, and will typically be anexplosion-proof box suitable for hazardous locations.

In addition, the power system and module should meet the requirementsfor a minimum of IPX5 (water spray) and IP6X (exposure to dust) ratingspublished by the International Electrotechnical Commission (“IEC”).Likewise, requirements for cable protection and pull-test requirements,excessive surface temperatures, and prevention of arc propagation underpotential failure modes are addressed.

A block diagram drawing of a power system is illustrated in FIG. 1 .Components include an environmentally sealed, nonincendive ac-dc powerconverter and a junction box suitably rated for an intended application.

Conventional physical realizations of transformer-rectifier (“TR”) unitsdesigned for hazardous environments are typically large, heavy, andexpensive. A TR unit designed to supply up to 2500 watts can occupy avolume greater than 4 feet by 4 feet by 6 feet (96 cubic feet) and weighhundreds of pounds. In addition to being large and heavy, conventionalTRs do not have a provision to electronically regulate and controldelivered output power.

Turning now to FIG. 1 , illustrated is a block diagram of an embodimentof a power system 100 in certified, explosion-proof housings. The powersystem 100 includes an enclosure 110 with components as set forth belowand a hazardous location (“HAZLOC”) environmentally sealed power module(“ESPM”) 120. The enclosure 110 includes a potentiometer in an enclosedcontainer (generally referred to as a potentiometer 130). Thepotentiometer 130 provides a local mechanism for controlling an outputvoltage or an output current (or a combination of the two or othercharacteristic) of the HAZLOC ESPM 120.

A power converter based on HFSM technology in the HAZLOC ESPM 120,preferably formed at least partially of an aluminum extrusion, replacesan ac, line-frequency transformer rectifier (“TR”) with a module that isa small fraction of the TR's size, weight, and cost. HFSM circuits alsoprovide an opportunity to locally or remotely electronically regulateand control delivered output power. However, circuit complexity involvedin HFSM products has previously precluded their implementation inenvironmentally challenging applications.

As illustrated in FIG. 1 , the enclosure 110 contains a Class 1 junctionbox 140 to enable an electrical connection to an ac power source. Avoltmeter 150 is configured to sense the input ac voltage to the HAZLOCESPM 120. An ammeter 160 is configured to sense an input current to theHAZLOC ESPM 120, and the enclosed potentiometer 130 is configured to seta reference voltage or current level or a combination thereof for theHAZLOC ESPM 120. The enclosure 110 with the aforementioned components iscoupled to system loads in a building structure, and wiring thatprovides electrical coupling to an ac power source and to the HAZLOCESPM 120.

The HAZLOC ESPM 120 is environmentally sealed and includes an ac-dcpower converter constructed with an HFSM design that provides highpower-conversion efficiency, small size, along with precise control ofdelivered power, current or voltage from the power convertercontrollable via an external interface. The switches of the powerconverter include a solid-state design with no internal mechanical orelectromechanical switches. The power converter meets the insulationintegrity and safety requirements stipulated in recognized safetystandards such as Underwriters Laboratories standard UL61010-1.

The electronic assemblies contained in the sealed aluminum HAZLOC ESPM120 are submersed in oil appropriately rated for electronics use.Encapsulation in oil achieves the dual purposes of heat management andenvironmental compatibility with IP65 requirements. The enclosure thathouses the power converter is formed with internal and external fins forthermal management. As thus realized, the power converter is suitablefor either an indoor or an outdoor location and in proximity to ahazardous environment. Field wiring is achieved though permanentlyattached cables that are mechanically affixed to the HAZLOC ESPM 120chassis and protected to meet cable pull-test and durabilityrequirements.

The hazardous location power system 100 is constructed with anenvironmentally sealed, nonincendive, ac-dc power converter in theHAZLOC ESPM 120 that provides desired power conversion and regulationfunctions. Provisions for system interface electrical connections aremade in certified, explosion-proof housings. The power system 100 isformed with the lockable potentiometer 130 housed in the Class 1,Division 1 box. The voltmeter 150 and ammeter 160 measure, respectively,voltage and current supplied to the power system 100.

The power system 100 employs a technology that adapts HFSM technology toenvironmentally challenging applications, especially those wherecompliance with safety agency hazardous location specifications, such asISA-12.12.01 or UL 121201, Nonincendive Electrical Equipment for use inClass I and II, Division 2 and Class III, Divisions 1 and 2 Hazardous(Classified) Locations. These specifications cover units in locationsmade hazardous by the presence of flammable gases, liquids, vapors, orfibers and where ignitable concentrations are not likely to exist undernormal operating conditions but can exist under certain conditions.

A target of the technology introduced herein is an electronic powersystem 100 that converts locally available input power (typically acutility power) to a power type more suitable to the end application(typically isolated, low voltage dc) in a manner that meets therequirements of typical hazardous location safety standards fornonincendive equipment. The power system 100 addresses requirements fora minimum of IPX5 (water spray) and IP6X (exposure to dust). Likewise,it also addresses requirements for cable protection and pull-testrequirements, excessive surface temperatures, and prevention of arcpropagation under potential failure modes.

Turning now to FIG. 2 , illustrated is a block diagram of an embodimentof a power system 200 in certified, explosion-proof housing. The powersystem 200 includes an enclosure 210 with a Class 1 junction box 240 toenable an electrical connection to an ac power source. The enclosure 210also includes a voltmeter 250 configured to sense the input ac voltageto a HAZLOC ESPM 220, and an ammeter 260 configured to sense an inputcurrent to the HAZLOC ESPM 220. The aforementioned components operatesimilarly to the analogous components described above with respect toFIG. 1 .

The power system 200 is coupled to a controller 235 (e.g., a computerrunning an energy management application) via a Class 1, Div-1 junctionbox 230 in the enclosure 210. The controller 235 manages the powersystem 200 by regulating an output voltage and/or an output current ofthe HAZLOC ESPM 220. While the power system 200 illustrates wiredconnectivity with the controller 235, it may also be possible to usewireless connectivity depending on the application. Thus, greaterflexibility for final deployment of a power system is achieved, whereinelectrical connections and external controls can be located locally orin a remote location from the hazardous environment.

Turning now to FIG. 3 , illustrated is a block diagram of an embodimentof a power system 300 in a wall-mount cabinet 310 fitted with cover 315.The power system 300 includes a HAZLOC ESPM 320 and a potentiometer inan enclosed container (generally referred to as a potentiometer 330).The potentiometer 330 provides a local mechanism for controlling anoutput voltage or an output current (or a combination of the two orother characteristic) of the HAZLOC ESPM 320. A Class 1 junction box 340enables an electrical connection to an ac power source. A voltmeter 350is configured to sense the input ac voltage to the HAZLOC ESPM 320. Anammeter 360 is configured to sense an input current to the HAZLOC ESPM320. The aforementioned components operate similarly to the analogouscomponents described above with respect to FIGS. 1 and 2 .

Turning now to FIG. 4 , illustrated is a block diagram of an embodimentof a power system 400 in a wall-mount cabinet 410 fitted with cover 415.The power system 400 includes a HAZLOC ESPM 420 in communication with acontroller 435 (e.g., a computer running an energy managementapplication) via a Class 1, Div-1 junction box 430 in the wall-mountcabinet 410. The controller 435 manages the power system 400 byregulating an output voltage and/or an output current of the HAZLOC ESPM420. While the power system 400 illustrates wired connectivity with thecontroller 435, it may also be possible to use wireless connectivitydepending on the application. Thus, greater flexibility for finaldeployment of a power system is achieved, wherein electrical connectionsand external controls can be located locally or in a remote locationfrom the hazardous environment.

A Class 1 junction box 440 enables an electrical connection to an acpower source. A voltmeter 450 is configured to sense the input acvoltage to the HAZLOC ESPM 420. An ammeter 460 is configured to sense aninput current to the HAZLOC ESPM 420. The aforementioned componentsoperate similarly to the analogous components described above withrespect to FIGS. 1, 2 and 3 .

Turning now to FIG. 5 , illustrated is a schematic diagram of anembodiment of a power converter (e.g., a switched-mode power converter500) employable with a hazardous location environmentally sealed powermodule. The power converter 500 converts an ac input voltage to anisolated and regulated dc output voltage. The power converter 500 isformed with a non-isolating, power-factor corrected (“PFC”) boostconverter stage (also referred to as a PFC boost converter stage 510)coupled to an input of an isolating, dc-dc converter stage (alsoreferred to as a dc-dc converter stage 550).

The PFC boost converter stage 510 is formed with a multistage input EMIfilter 515, formed with two common-mode chokes coupled to differentialmode capacitors, coupled in turn to four-diode bridge 520 that producesa unipolar output voltage with a waveform somewhat similar to that of arectified sinewave voltage. The unipolar output voltage of the PFC boostconverter stage 510 is coupled to the input of boost converter stage 525formed with an input inductor 530, a power switch (e.g., a metal-oxidesemiconductor field-effect transistor (“MOSFET”) 535) and a diode Dl.The output voltage of the PFC boost converter stage 510 is filtered bythe capacitor bank 540. A PFC control and drive circuit 545 provides acontrol signal to control an operation of the MOSFET 535.

A non-isolated dc output voltage of the PFC boost converter stage 510 isprovided to an input of the dc-dc converter stage 550. The input voltageof the dc-dc converter stage 550 is switched at a high frequency (e.g.,a 100 kilohertz (“kHz”) or more by power switches (e.g., MOSFETs 555),controlled by switch drive circuit 560, and the resulting switchedvoltage waveform is coupled to input windings of isolating transformers565. An output voltage of the isolating transformers 565 is coupled todiode bridge 570 to produce a dc output voltage from the dc-dc converterstage 550. This dc output voltage is filtered by low-pass filter 575formed with an inductor and four capacitors, followed by common-modeinductor filter 580. A dc-dc converter controller 585 receives anisolated and controlled dc output voltage as a feedback mechanism tocontrol the MOSFETs 555 via the switch drive circuit 560 The net resultis power-factor corrected ac current is drawn from the ac input voltage,which is then converted to an isolated and regulated dc output voltageof the power converter 500.

Turning now to FIG. 6 , illustrated is an isometric diagram of anembodiment of a hazardous location (“HAZLOC”) environmentally sealedpower module (“ESPM”) 600. The HAZLOC ESPM 600 includes an extruded tube(e.g., an extruded aluminum tube 610) with external fins 620 for thermalmanagement and a mounting plate 630. An end cap 640 is attached to oneend of the extruded aluminum tube 610. A heavy-duty strain reliefconduit fitting 650 terminates the jacket of an electrical cable 660.The extruded aluminum tube 610 can be substantially filled with oil forthermal management. Ends of the extruded aluminum tube 610 are sealedliquid-tight with plates and O-rings.

Turning now to FIG. 7 , illustrated is a partially exploded isometricdiagram of an embodiment of a hazardous location (“HAZLOC”)environmentally sealed power module (“ESPM”) 700. A bottom plate 705with an O-ring 710 is configured to be coupled to a first opposingsurface of and provide a liquid-tight and hermetic seal for an extrudedtube (e.g., an extruded aluminum tube 715) with internal fins 720 andexternal fins 725. A power converter 730 on a printed circuit board 735is configured to be located within a compartment (or internal slots 740)defined by the internal fins 720. A cable interface plate 745 with cableglands (one of which is designated 750) is configured to be coupled to asecond opposing surface of and provide a liquid-tight and hermetic sealfor the extruded aluminum tube 715. An end cap 755 is configured to beattached to the cable interface plate 745 that includes a heavy-dutystrain relief conduit fitting 760 terminating the jacket of anelectrical cable 765. The extruded aluminum tube 715 can besubstantially filled with oil for thermal management. Ends of theextruded aluminum tube 715 are sealed liquid-tight with respectiveplates and O-rings.

An aspect of the HAZLOC ESPM 700 is the ability to utilize commercialcomponents, normally intended for usage in air, in an oil-encapsulatedenvironment. This allows electronic assemblies normally intended forair-cooling to be easily adapted to an encapsulated assembly which isfully weather-proof. The use of oil is especially useful whenconsidering magnetic components as these usually generate significantheat and are irregularly shaped, making it difficult to conduct heatfrom them via a hard surface. The encapsulating oil is able to penetratethe magnetic elements and transport the heat generated to the externalfins 725 of the extruded aluminum tube 715 via interaction with theinternal fins 720 illustrated in FIG. 7 .

Turning now to FIG. 8 , illustrated is an exploded isometric diagram ofan embodiment of a hazardous location (“HAZLOC”) environmentally sealedpower module (“ESPM”) 800. A bottom plate 805 includes a depression 807to receive an O-ring 810 and is configured to be coupled (via matingscrews 808) to a first opposing surface 815 of and provide aliquid-tight and hermetic seal for an extruded tube (e.g., an extrudedaluminum tube 820) with internal fins 825 and external fins 830. A powerconverter 832 is configured to be located within a compartment (orinternal slots 835) defined by the internal fins 825.

A cable interface plate 840 includes a depression 845 to receive asecond O-ring 850 and is configured to be coupled to a second opposingsurface 855 of and provide a liquid-tight and hermetic seal for theextruded aluminum tube 820. The cable interface plate 840 is formed withthree liquid-tight/hermetic cable glands (one of which is illustrated inFIG. 8 as cable gland 860) that fit in holes in the cable interfaceplate 840 such as hole 865 that enables an electrical cable 862 toextend into and out of the extruded aluminum tube 820 for the powerconverter 832 therein. The liquid-tight cable glands 860 are preferablysealed with epoxy.

An end cap 870 is configured to be attached to the cable interface plate840 and the second opposing surface 855 (via the cable interface plate840) with mating screws 875. The end cap 870 is configured to accept aconduit fitting to enable an electrical cable to be routed from withinthe end cap 870 to an external electrical connection point. The end cap870 serves to provide protection for cables that exit from the sealedHAZLOC ESPM 800, as well as provide a mounting location for a metalconduit fitting to route cables to external electrical connectionpoints.

The extruded aluminum tube 820 can be substantially filled with oil forthermal management. The oil may include a bio-based natural esterdielectric coolant, for example, Envirotemp™ FR3™ fluid produced byCargill. The internal fins 825 serve to capture heat by employing anelectrically insulating encapsulating oil which circulates due toconvection forces as the power converter 832 heats up. The extrudedaluminum tube 820 acts as an electrical shield for high frequencyswitch-mode waveforms produced by the power converter 832. The externalfins 830 dissipate heat generated by the power converter 832 via freeconvection of surrounding air. The extruded aluminum tube 820 is alsoformed with extruded-in-place mounting feet 880. The extruded aluminumtube 820, the internal fins 825, the external fins 830, the mountingfeet 880, and the internal slots 835 can be formed in one extrusionoperation.

Turning now to FIG. 9 , illustrated is a plan view of an embodiment ofan end cap 900. The end cap 900 includes a mating flange 910 with matingholes (one of which is designated 920). The end cap 900 also includes aconduit fitting 930 sized to mount in a hole 940 in the end cap 900. Theconduit fitting 930 is configured to terminate the jacket of anelectrical cable.

Turning now to FIG. 10 , illustrated is a flow diagram of an embodimentof a method 1000 of forming a hazardous location (“HAZLOC”)environmentally sealed power module (“ESPM”). When describing featuresof the HAZLOC ESPM (e.g., HAZLOC ESPM 800), the description of themethod 1000 below will refer to representative FIGUREs above withcorresponding reference numbers of the features. The method begins at astart step or module 1010. At a step or module 1020, the method 1000includes providing an extruded tube (e.g., an aluminum extruded tube)formed with an internal fin and an external fin and a first opposingsurface and a second opposing surface defining ends of the extrudedtube. (See, e.g., FIG. 8 , an extruded tube 820, internal fins 825,external fins 830, a first opposing surface 815, and a second opposingsurface 855.) The first opposing surface and the second opposing surfaceof the extruded tube may be machined flat. The extruded tube may alsoinclude extruded in-place mounting feet. (See, e.g., FIG. 8 , extrudedin-place mounting feet 880.) The extruded tube, the internal fin, theexternal fin, and the extruded in-place mounting feet may be formed inone extrusion operation.

At a step or module 1030, the method 1000 includes placing a powerconverter (e.g., a switched-mode power converter 500 of FIG. 5 ) withinan internal slot of the extruded tube. (See, e.g., FIG. 8 , a powerconverter 832, an internal slot 835, and the extruded tube 820.) Themethod 1000 continues by providing a first liquid-tight fluid seal atthe first opposing surface for an electrically insulting oil (e.g.,including a bio-based natural ester dielectric coolant) encapsulatingthe power converter within the internal slot at a step or module 1040.The first liquid-tight fluid seal may be provided by a bottom plateformed with a first depression configured to receive a first O-ringdisposed between the first opposing surface and the first depression.(See, e.g., FIG. 8 , a bottom plate 805, a first depression 807, a firstO-ring 810, and the first opposing surface 815.) The bottom plate may besecured to the first opposing surface with mating screws. (See, e.g.,FIG. 8 , mating screws 808.)

At a step or module 1050, the method 1000 includes providing a secondliquid-type fluid seal at the second opposing surface for theelectrically insulting oil encapsulating the power converter within theinternal slot. The second liquid-tight fluid seal may be provided by acable interface plate formed with a second depression configured toreceive a second O-ring disposed between the second opposing surface andthe second depression. (See, e.g., FIG. 8 , a cable interface plate 840,a second depression 845, a second O-ring 850, and the second opposingsurface 855.) The method 1000 continues with providing aliquid-tight/hermetic cable gland within a hole of the cable interfaceplate to enable an electrical cable to extend into and out of the HAZLOCESPM at a step or module 1060. (See, e.g., FIG. 8 , aliquid-tight/hermetic cable gland 860, a hole 865, the cable interfaceplate 840, and an electrical cable 862.) At a step or module 1070, themethod 1000 includes sealing the liquid-tight/hermetic cable glandwithin the hole with epoxy. (See, e.g., FIG. 8 , theliquid-tight/hermetic cable gland 860, and the hole 865.)

At a step or module 1080, the method 1000 includes mating an end cap tothe cable interface plate. (See, e.g., FIG. 8 , the cable interfaceplate 840, and an end cap 870.) The end plate and the cable interfaceplate may be secured to the second opposing surface with mating screws.(See, e.g., FIG. 8 , mating screws 875.) The method 1000 continues withenabling an electrical cable to be routed from within the end cap to anexternal connection point via a conduit fitting coupled to the end capat a step or module 1090. (See, e.g., FIG. 7 , an end cap 755, a conduitfitting 760, and an electrical cable 765.) The method 1000 ends at anend step or module 1095. After the HAZLOC ESPM is formed, the HAZLOCESPM may be controlled by a controller such as a remote controller.(See, e.g., FIG. 2 , controller 235, FIG. 4 , controller 435.)

Although the embodiments and its advantages have been described indetail, it should be understood that various changes, substitutions, andalterations can be made herein without departing from the spirit andscope thereof as defined by the appended claims. For example, many ofthe features and functions discussed above can be implemented insoftware, hardware, or firmware, or a combination thereof. Also, many ofthe features, functions, and steps of operating the same can bereordered, omitted, added, etc., and still fall within the broad scopeof the various embodiments.

Moreover, the scope of the various embodiments is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein can be utilized as well. Accordingly, the appendedclaims are intended to include within their scope such processes,machines, manufacture, compositions of matter, means, methods, or steps.

What is claimed is:
 1. A power module, comprising: an extruded tubeformed with an internal fin and an external fin and a first opposingsurface and a second opposing surface defining ends of said extrudedtube, said extruded tube including an internal slot for housing a powerconverter; a bottom plate formed with a first depression configured toreceive a first O-ring disposed between said first opposing surface andsaid first depression to provide a first liquid-tight fluid seal at saidfirst opposing surface for an electrically insulating oil encapsulatingsaid power converter within said internal slot; and a cable interfaceplate formed with a second depression configured to receive a secondO-ring disposed between said second opposing surface and said seconddepression to provide a second liquid-type fluid seal at said secondopposing surface for said electrically insulating oil encapsulating saidpower converter within said internal slot.
 2. The power module asrecited in claim 1 further comprising an end cap configured to mate withsaid cable interface plate and accept a conduit fitting to enable anelectrical cable to be routed from within said end cap to an externalconnection point.
 3. The power module as recited in claim 1 wherein saidcable interface plate is further configured to receive aliquid-tight/hermetic cable gland that enables an electrical cable toextend into and out of said power module.
 4. The power module as recitedin claim 3 wherein said liquid-tight/hermetic cable gland is sealed withepoxy.
 5. The power module as recited in claim 1 wherein said powerconverter is configured to be controlled by a controller remote fromsaid power module.
 6. The power module as recited in claim 1 whereinsaid electrically insulating oil comprises a bio-based natural esterdielectric coolant.
 7. The power module as recited in claim 1 whereinsaid first opposing surface and said second opposing surface of saidextruded tube are machined flat.
 8. The power module as recited in claim1 wherein said extruded tube comprises aluminum.
 9. The power module asrecited in claim 1 wherein said extruded tube is further formed with anextruded in-place mounting feet.
 10. The power module as recited inclaim 9 wherein said extruded tube, said internal fin, said external finand said extruded in-place mounting feet are formed in one extrusionoperation.
 11. A method of forming a power module, comprising: providingan extruded tube formed with an internal fin and an external fin and afirst opposing surface and a second opposing surface defining ends ofsaid extruded tube; placing a power converter within an internal slot ofsaid extruded tube; providing a first liquid-tight fluid seal at saidfirst opposing surface for an electrically insulating oil encapsulatingsaid power converter within said internal slot with a bottom plateformed with a first depression configured to receive a first O-ringdisposed between said first opposing surface and said first depression;and providing a second liquid-type fluid seal at said second opposingsurface for said electrically insulating oil encapsulating said powerconverter within said internal slot with a cable interface plate formedwith a second depression configured to receive a second O-ring disposedbetween said second opposing surface and said second depression.
 12. Themethod as recited in claim 11 further comprising mating an end cap tosaid cable interface plate, enabling an electrical cable to be routedfrom within said end cap to an external connection point via a conduitfitting coupled to said end cap.
 13. The method as recited in claim 11further comprising providing a liquid-tight/hermetic cable gland withina hole of said cable interface plate to enable an electrical cable toextend into and out of said power module.
 14. The method as recited inclaim 13 further comprising sealing said liquid-tight/hermetic cablegland within said hole with epoxy.
 15. The method as recited in claim 11further comprising controlling said power converter with a controllerremote from said power module.
 16. The method as recited in claim 11wherein said electrically insulating oil comprises a bio-based naturalester dielectric coolant.
 17. The method as recited in claim 11 whereinsaid first opposing surface and said second opposing surface of saidextruded tube are machined flat.
 18. The method as recited in claim 11wherein said extruded tube comprises aluminum.
 19. The method as recitedin claim 11 further comprising providing extruded in-place mounting feetfor said extruded tube.
 20. The method as recited in claim 19 whereinsaid extruded tube, said internal fin, said external fin and saidextruded in-place mounting feet are formed in one extrusion operation.